SSTI

Question 1

Normal protecting factors of skin

Answer 1

1) Dry surface - Inhibits bacterial growth
2) Fatty acids
3) Acidic pH (~5.6)
4) Renewal of epidermis - Dead skin cells & bacteria removed from skin surface
5) Low temperature

–> Inhibits excessive bacterial growth & entry into deeper layers

Question 2

Pathophysiology of SSTIs

Answer 2

1) Penetration of normal skin bacteria into deeper layers
2) Introduction of other bacteria
3) Excess bacteria growth

Question 3

Predisposing factors

Answer 3

• High bacteria innocula
• Excessive moisture
• Reduced blood supply
• Presence of bacterial nutrients
• Poor hygiene
• Sharing of personal items

Question 4

How are SSTIs classified?

Answer 4

• Severity/extent
• Depth of infection
• Presence/absence of pus discharge
• Microbiology
• Anatomical site

Question 5

Impetigo & Ecthyma classification

Answer 5

• Usually managed as outpatient

Severity: Mild
Depth: Uncomplicated
Discharge/ Purulent/Non-purulent
Micriobiology: Primary

Question 6

Clinical presentation of Impetigo & Ecthyma

Answer 6

Impetigo: Most common in children/face/extremities as fluid-filled vesicles
Ecthyma: Deeper than impetigo, scarring common

Question 7

Microbiology of Impetigo & Ecthyma

Causative microbes & cultures

Answer 7

Causative microbes:

i) Staph aureus - bullous form caused by S.Aureus
ii) B-hemolytic Streptococci (eg. Strep pyrogens)

Culture:
- Usually treated w/o but can culture if have pus

Question 8

Impetigo treatment

Answer 8

Topical Mupirocin BD x 5days

Oral antibiotic only if severe cases

Question 9

Ecthyma treatment

Answer 9

Empiric:

i) Cephalexin/Cloxacillin
ii) Clindamycin (penicillin allergy)

Culture-directed:

i) Pen VK (S. pyrogens)
ii) Cephalexin/Cloxacillin (MSSA)

Duration: x 7days

Question 10

Risk factors for purulent SSTIs

Answer 10

Close physical contact
Crowded living conditions
Poor personal hygiene
Sharing personal items

Question 11

Microbiology of Purulent SSTIs

Causative microbes & cultures

Answer 11

Causative microbe: Staph aureus
(Cutaneous abscess may be polymicrobial)

Usually treated w/o culture

Question 12

Treatment of Purulent SSTIs

Answer 12

I&D

Adjunctive systemic antibiotics if:

• Unable to drain completely/ lack of response
• Extensive disease involving several sites
• Extremes of age
• Immmunosupressed
• Signs of SIRS

Question 13

Criteria for SIRS

Answer 13

Temp > 38C or < 36C
HR > 90 beats/min
RR > 24 beats/min
WBC > 12 X 10^9 or < 4 x 10^9

Question 14

Antibiotics Treatment for Purulent SSTIs

Furuncles, carbuncles

Answer 14

MSSA only:

• PO Cloxacillin
• PO Cephelaxin
• IV Cefazolin

MSSA, MRSA:

• PO Clindamycin
• PO Cotrimoxazole
• PO Doxycycline

Duration: 5-7 days (outpatient)
7-14 days (inpatient)

Question 15

Clinical presentation of Cellulitis vs Erysipelas

Answer 15

Cellulitis: Poorly demarcated area, purulent/non-purulent

• Acute inflmm of epidermis, dermis & sometimes superficial fascia
• Bacteria can invade lymphatic tissue & blood

Erysipelas: Sharply demarcated area with raised border
- Affects up to superficial dermis & lymphatic tissue

Question 16

Complications of Cellulitis vs Erysipelas

Answer 16

• Bacteremia
• Endocarditis
• Toxic shock
• Glomerulonephritis
• Lymphedema (Buildup of fluid due to blockage of lymphatic system)
• Osteomyelitis (Inflmm/swelling in bone)
• Necrotizing soft-tissue infections

Question 17

Microbiology of Cellulitis vs Erysipelas

Causative microbes & cultures

Answer 17

Causative microbe:

i) Staph aureus (purulent)
ii) B-hemolytic strep (for Erysipelas)

Cultures:

• Not routinely recommended
• Reasonable if purulent infections after I&D/ immunosuppressed/ SIRS
• -> tissue sample valuable

Question 18

Treatment of non-purulent Cellulitis/ Erysipelas

Answer 18

Mild: Treat for Streptococcus spp

i) PO Penicillin VK
ii) PO Cloxacillin
iii) PO Cephalexin
iv) PO Clindamycin

Moderate: Treat for Strep/ S.Aureus
1 SIRS criteria –> Treat like mild

2 SIRS criteria

i) IV Cefazolin
ii) IV Pen G
iii) IV Clindamycin

Severe: Treat for Strep/ S.Aureus/ Gram(-)
2 SIRS + hypotension/rapid progression/immunosupressed/comorbidity
i) IV Pip/Tazo
ii) IV Cefepime
iii) IV Meropenem

if MRSA risk factors, add:

• IV Vancomycin
• IV Daptomycin
• IV Linezolid

Question 19

MRSA Risk factors

Answer 19

i) Immunosupression
ii) Critically ill
iii) Previously failed antibiotics w/o MRSA activity

Question 20

Treatment of purulent Cellulitis/ Erysipelas

Answer 20

Mild: Streptococcus spp/S. Aureus

i) PO Cephalexin
ii) PO Cloxacillin
iii) PO Clindamycin

if MRSA risk factors, add:

• PO Cotrimoxazole
• PO Clindamycin
• PO Doxycycline

Moderate: Streptococcus spp/S. Aureus
1 SIRS criteria –> Treat like mild

2 SIRS criteria

i) IV Cloxacillin
ii) IV Cefazolin
iii) IV Clindamycin

if MRSA risk factors, add:

• IV Vancomycin
• IV Daptomycin
• IV Linezolid

Severe: Treat for Strep/S.Aureus/Gram(-) including P. aeruginosa
2 SIRS + hypotension/rapid progression/immunosupressed/comorbidity

i) IV Pip/Tazo
ii) IV Cefepime
iii) IV Meropenem

if MRSA risk factors, add:

• IV Vancomycin
• IV Daptomycin
• IV Linezolid

Question 21

Organism for animal bite wounds

Answer 21

Pasteurella multocida

Question 22

Organism for human bite wounds

Answer 22

Eikenella corrodens

Question 23

Organism for oral anaerobes

Answer 23

Prevotella spp, Peptostreptococcus spp

Question 24

Treatment of cellulitis from bite wounds?

Answer 24

i) Augmentin
ii) Ceftriaxone/Cefuroxime + clindamycin/metronidazole
iii) Ciprofloxacin/Levofloxacin + clindamycin/metronidazole

Question 25

Pathophysiology of DFI

Answer 25

1) Neuropathy - Peripheral: Decreased pain sensation & response - Motor: Motor imbalance - Autonomic: Increased dryness, cracks & fissures 2) Vasculopathy - Early artherosclerosis - PVD - Worsened by hyperglycemia & dyslipidemia 3) Immunopathy - Impaired immune response - Increased susceptibility to infections - Worsened by hyperglycemia - -> Ulcer/wound formation - -> Bacterial colonization/ proliferation/ penetration - -> DFI

Question 26

Causative organism of DFI/PU

Answer 26

- Typically polymicrobial i) Staph aureus & Strep *Most common* ii) Gram (-) [Chronic wounds/ Previously treated] - E.coli, Klebsiella, Proteus iii) Anaerobes [Ischaemic/ Necrotic wounds] - Peptostreptococcus spp, Veilonella spp, Bacteriodes spp

Question 27

Cultures for DFI

Answer 27

Mild: optional Moderate: Deep tissue cultures after cleansing & before starting antibiotics. Avoid skin swabs Do not culture uninfected wounds

Question 28

Treatment of DFI/PU

Answer 28

``` Mild x 1-2 weeks: Streptococcus spp/S. Aureus (Erythema < 2cm) i) PO Cephalexin ii) PO Cloxacillin iii) PO Clindamycin ``` if MRSA risk factors, add: - PO Cotrimoxazole - PO Clindamycin - PO Doxycycline Mod x 1-3weeks : Strep/S. Aureus/Gram -ve (+- P. aeruginosa)/Anaerobes (Erythema > 2cm + No signs of systemic infection) i) IV Augmentin ii) IV Ceftriaxone ** ( + Clindamycin/Metronidazole) if MRSA risk factors, add: - IV Vancomycin - IV Daptomycin - IV Linezolid Severe x 2-4weeks: Strep/S. Aureus/Gram -ve (P. aeruginosa)/Anaerobes (Signs of SIRS) i) IV Pip/Tazo ii) IV Mereopenem iii) IV Cefepime ** ( + Clindamycin/Metronidazole) if MRSA risk factors, add: - IV Vancomycin - IV Daptomycin - IV Linezolid

Question 29

Adjunctive measures for DFI

Answer 29

Wound care - Debridement - "Off-loading" [Supportive shoes] - Apply dressings that promote a healing environment & control excess exudation Foot care - Daily inspection - Prevent wounds & ulcers

Question 30

How does Pressure Ulcers come about?

Answer 30

- Moisture - Pressure (Amount & duration) - Shearing force - Friction

Question 31

Risk factors for pressure ulcers

Answer 31

- Reduced mobility - Debilitated by severe chronic disease - Reduced consciousness - Sensory & autonomic impairment - Extremes of age - Malnutrition

Question 32

Cultures for PU?

Answer 32

- Recommend deep tissue cultures/biopsy specimens | - Avoid skin swabs

Question 33

Adjunctive measures for pressure ulcers

Answer 33

- Debridement of infected or necrotic tissue - Local wound care (Normal saline preferred) - Relief of pressure (Turn or reposition every 2hrs, also impt for prevention)